The structure of metallo-bleomycin (M-BLM) on DNA has been the subject of intense investigation and various spectroscopic methods have been used to delineate the structure of the bound form. We have applied ESR methods using the highly oriented DNA-fibers and evaluated the geometrical parameters for the orientation of the metal binding domain of Cu(II)-BLM and O2-Co(II)-BLM on A-form DNA-fibers.